On those occasions when I needed to reform or create a sight dovetail, back in my formative gunsmith days, my tools were as many hacksaw blades that when stacked together and mounted on the same hacksaw frame carefully made the vertical slot to near dimensions, followed by a "safe" triangular file, or a standard file ground to produce the dovetail angle...
used VERY carefully by my calibrated hand. If I made a mistake, and there were a few
, we got the welder out and filled the dovetail and started over...
I did have a dovetail cutter for a 1911A1 rearsight dovetail at one time, but only used it once...